1. Field of the Invention
The present invention relates to a pulsating combustion system comprising two parallel-connected pulsating combustors, and also to a method of starting the pulsating combustion system.
2. Description of the Related Art
A pulsating combustor is advantageous over the ordinary burner in various respects, such as thermal efficiency, content of harmful substance in the exhaust gas, and the like.
Most pulsating combustors comprises a combustion chamber having an exhaust port, a fuel passage through which a fuel is supplied into the combustion chamber, an air passage through which air is supplied into the combustion chamber, a tail pipe connected to the exhaust port of the combustion chamber, a flap valve located within the air passage, and an ignitor for igniting the air-fuel mixture in the combustion chamber to start the combustor.
When the mixture gas, i.e., the air-fuel mixture, is ignited, it is explosively combusted. As a result, the pressure within the combustion chamber increases abruptly, automatically closing the flap valve located in the air passage. Simultaneously, the combustion gas is exhausted at high speed through the exhaust port of the combustion chamber. As a result of this gas-exhaustion, a negative pressure is generated within the combustion chamber. Hence, the flap valve opens, allowing both air and fuel to flow into the chamber. When the air and the fuel flow into the chamber, each in a predetermined amount, and are thoroughly mixed, the resultant mixture gas is combusted explosively, ignited by the flame remaining in the combustion chamber. The combustion is repeatedly performed in the combustion chamber. This combustion is an intermittent or pulsative one. The pulsating combustor inevitably makes much noise during operation.
A pulsating combustion system has been invented which is designed to make less noise during operation. This system comprises a pair of pulsating combustors connected in parallel to each other. An aerodynamic valve, whose forward flow efficiency is greater than the backward flow efficiency, is provided within the air passage of either pulsating combustor. The aerodynamic valve cannot prevent the backflow of air completely. In other words, it performs an incomplete backflow prevention. Due to this incomplete backflow prevention, the pressure changes in the combustion chambers of the combustors interfere with each other. As a result of this, the gas intake, combustion-explosion, and gas exhaustion in the first pulsating combustor can be 180.degree. out of phase with those taking place in the second pulsating combustor. Thus, the pressure changes in the combustion chamber of the first combustor are cancelled out by those in the combustion chamber of the second combustor, whereby the pulsating combustion system makes less noise than the conventional pulsating combustor.
To start the pulsating combustion system, the residual gas is purged from the combustion chambers of both pulsating combustors, and then the ignitors of the both pulsating combustors are operated. In this condition, the mixture gas is introduced into the combustion chambers to combusted explosively. This method of ignition cannot ignite the mixture gas in one chamber, with a time lag of a few milliseconds with respect to the ignition in the other combustion chamber. Consequently, the gas intake, combustion-explosion, and gas exhaustion in one combustor cannot be set quickly at 180.degree. out of phase with those taking place in the other combustor. It inevitably takes long until the pulsating combustors come to perform combustion in completely out of phase by 180.degree., or the pulsating combustors alternately achieve explosions but at two low a frequency. In short, the pulsating combustion system fails to operate as stably as is desired.